The Zn Vacancy-Mediated De-Accumulation Based Process for Hydrogen Production Performance Promotion of 1D Zn─Cd─S Nanorods.

Due to their anisotropy, 1D semiconductor nanorod-based materials have attracted much attention in the process of hydrogen production by solar energy. Nevertheless, the rational design of 1D heterojunction materials and the modulation of photo-generated electron-hole transfer paths remain a challenge. Herein, a ZnxCd1-xS@ZnS/MoS2 core-shell nanorod heterojunction is precisely constructed via in situ growth of discontinuous ZnS shell and MoS2 NCs on the Zn─Cd─S nanorods. Among them, the Zn vacancy in the ZnS shell builds the defect level, and the nanoroelded MoS2 builds the electron transport site. The optimized photocatalyst shows significant photocatalytic activity without Platinum as an auxiliary catalyst, mainly due to the new interfacial charge transfer channel constructed by the shell vacancy level, the vertical separation and the de-accumulation process of photo-generated electrons and photo-generated holes. At the same time, spectral analysis, and density functional theory (DFT) calculations fully prove that shortening difference of speed between the photogenerated electron and hole movement process is another key factor to enhance the photocatalytic performance. This study provides a new path for the kinetic design of enhanced carrier density by shortening the carrier retention time of 1D heterojunction photocatalysts with improved photocatalytic performance.

Interfacial Nucleation Mechanism of Water-Soluble Ag-In-S Quantum Dots at Room Temperature and Their Visible Light Catalytic Performance.

A novel interfacial reaction nucleation mechanism for the preparation of water-soluble Ag-In-S quantum dots (AIS QDs) was proposed in which interfacial acid regulates the concentration of hydroxide ions outside the complex and sulfur sources attack cations at the interface of the complex, covalent bonds between cations and sulfur sources are formed at the interface of the complex, and the nucleation and growth of crystals is finished at room temperature. By bypassing the heating process normally necessary for crystal nucleation and growth, AIS QDs can be produced on a large scale under simple, mild conditions. At the same time, the characteristics of this mechanism enable AIS QDs to be directly synthesized in an organic pollutant solution. This study represents a significant advance in the mechanism of crystal synthesis and contributes to the photocatalytic decomposition of organic pollutants from theory to practice.

Ni(OH)2-derived lamellar MoS2/Ni3S2/NF with Fe-doped heterojunction catalysts for efficient overall water splitting.

Heterostructures formed by combining semiconductor materials with different band structures can provide work functions, d-band positions and electronic properties different from bulk materials and are considered as an effective strategy to improve the catalytic activity through electronic modification. In this study, an efficient MoS2/Fe-Ni3S2/NF heterojunction material was prepared by a two-step hydrothermal method. With the help of flake Ni(OH)2 synthesized in the first step, growth sites were provided for flake Ni3S2. The electronic structure of Ni3S2 was optimized by Fe doping, while the construction of the MoS2/Fe-Ni3S2 heterostructure allowed the catalyst to expose more active sites. MoS2/Fe-Ni3S2/NF exhibited a small charge transfer resistance and excellent electrocatalytic performance. At a current density of 10 mA cm-2, only low overpotentials of 148 mV and 118 mV were required for the oxygen precipitation reaction (OER) and hydrogen precipitation reaction (HER), respectively. Notably, when MoS2/Fe-Ni3S2/NF is used as the anode and cathode for overall hydrolysis, only 1.51 V is required to reach a current density of 10 mA cm-2, demonstrating its great potential for application in hydrolysis. This work provides a feasible idea for the rational construction of non-precious metal bifunctional electrocatalysts with excellent performance.

Improving photocatalytic hydrogen production by switching charge kinetics from type-I to Z-scheme via defective engineering.

By providing the spatial separation of the active sites and retaining high oxidative and reducing capacity, the direct Z-scheme heterostructure is considered the most potential structure for yielding photo-electric response. However, challenges still exist in the directional transfer of charge carriers between two semiconductors in direct Z-scheme structures. In this regard, by constructing the Vzn defect and p-n junction, a direct Z-scheme ZnxCd1-xS@ZnS-NiS heterostructure was obtained for the regulated electronic structure, which ensured high-yield hydrogen properties. The Zn vacancy in the partially-coated ZnS shell led to the Vzn energy level, and the addition of NiS led to the p-n structure, which caused a drastic downshift of the band edge potentials in comparison to that of pristine CdS. This variation gave rise to a staggered band edge alignment between ZnxCd1-xS and NiS, resulting in the variation of charge transfer kinetics from type-I to direct Z-scheme. Through careful characterization, it was found that the optimal photocatalytic hydrogen precipitation activity reached 16 683.6 µmol g-1 h-1, which was 70 times that of CdS, and this improvement was considered to form a spatial barrier, providing a clear direction and path for carrier transmission.